Which instrument replaced the Wide Field and Planetary Camera 2 on Hubble?

The Wide Field Camera 3 replaced the Wide Field and Planetary Camera 2 on the Hubble Space Telescope. Astronauts installed WFC3 during the first spacewalk of Space Shuttle Atlantis mission STS-125 on May 14, 2009.

WFPC2 had been installed in 1993 and became famous for producing many of Hubble’s early iconic images, including the original Hubble Deep Field. It also contained corrective optics that compensated for the flaw in Hubble’s primary mirror, making it an especially important instrument during the telescope’s early years.

WFC3 expanded Hubble’s imaging capabilities with separate ultraviolet/optical and near-infrared channels. Its detectors cover wavelengths from roughly 200 to 1,700 nanometers, allowing astronomers to study objects across a much broader portion of the electromagnetic spectrum.

The other options are Hubble instruments, but they are not the direct replacement named in the question. The Advanced Camera for Surveys is another imaging instrument, while COS and STIS are spectrographs designed primarily to split light into spectra rather than create broad astronomical images.